Effect of particle granularity on smoldering fire in wood chips made from wood waste: An experimental study

Abstract

Fires in wood waste storages cause financial losses, are difficult to extinguish, and emit large amounts of fire effluents. The mechanisms related to fires in wood chip piles are not well elucidated. To find suitable preventive measures for handling such fires in wood waste, a better understanding of the physical properties of wood waste is needed. The present study investigates how granularity affects mechanisms of smoldering fire and transition to flaming in wood chip piles. Eighteen experiments with samples inside a top-ventilated, vertical cylinder were conducted. Heating from underneath the cylinder induced auto-ignition and smoldering fire, and temperatures and mass loss of the sample were measured. The results showed that granularity significantly affects the smoldering fire dynamics. Material containing larger wood chips (length 4-100 mm) demonstrated more irregular temperature development, higher temperatures, faster combustion, and higher mass losses than material of smaller wood chips (length <4 mm). The larger wood chips also underwent transition to flaming fires. Flaming fires were not observed for small wood chips, which instead demonstrated prolonged and steady smoldering propagation. The differences are assumed to be partly due to the different bulk densities of the samples of large and small wood chips affecting the ventilation conditions. Increased knowledge about these combustion processes and transition to flaming is vital to develop risk-reducing measures when storing wood chips made from wood waste in piles.

Experimental Design for the Propagation of Smoldering Fires in Corn Powder and Cornflour

“…First, the smaller the particle size, the larger the surface area and the greater the oxygen attack to the oxidation step. Therefore, the smoldering reaction in corn flour samples develops faster than in corn powder samples, which perfectly agrees with other literature experiments, demonstrating that granularity significantly affects the smoldering dynamics [17].…”

“…After the burning process, part of the material turned to ashes and char residue (E) or if the burning was incomplete, unburnt material. [17], the appearance of a glowing mass may occur during the smoldering process, which was also observed during some experiments (C), especially experiments with dry corn flour. Additionally, the presence of smoke (D) was observed during the whole process.…”

“…Chunmiao et al [16] in their studies proved that increasing the particle size of magnesium powder from 6 to 173 µm increased the minimum ignition temperature and increasing the thickness of the dust layer decreased this temperature as well. Sesseng et al [17] performed some experiments with wood chips to evaluate how the granularity affects smoldering fire. All the aforementioned studies and other similar works elucidated the importance of studying the particle size and the minimum temperature at which dust layers or material piles ignite and can lead to smoldering fires.…”

Facile fabrication of a novel self-healing and flame-retardant hydrogel/MXene coating for wood

“…As a green, renewable and lightweight building material, wood has always attracted people’s attention 1 – 5 . However, its intrinsic high flammability brings about fire hazards which tends to cause huge economic losses and casualties 6 – 9 . Various methods have been developed to improve fire safety of wood, among which, flame-retardant coating is the most striking strategy as it could be easily applicable on wood 10 – 13 .…”